﻿#define _CRT_SECURE_NO_WARNINGS 1

//动态规划第四题
//04.斐波那契数列模型_解码方法_C++
//https://leetcode.cn/problems/decode-ways/description/


class Solution {
public:
    int numDecodings(string s) {
        int n = s.size();
        vector<int> dp(n + 1);
        dp[0] = 1;
        dp[1] = (s[0] != '0');

        for (int i = 2; i <= n; i++) {
            if (s[i - 1] != '0') {
                dp[i] += dp[i - 1];
            }

            int t = (s[i - 2] - '0') * 10 + (s[i - 1] - '0');

            if (t >= 10 && t <= 26) {
                dp[i] += dp[i - 2];
            }
        }

        return dp[n];
    }
};
